This invention relates to a ballistic laminate structure in sheet form, a ballistic panel constructed of a plurality of the sheets, a ballistic garment constructed of one or more of the ballistic panels, and a method of fabricating a ballistic laminate structure.
Numerous ballistic laminates are known, for example, those disclosed in U.S. Pat. Nos. 4,916,000, 4,079,161, 4,309,487, and 4,213,812. Prior art laminates have been constructed of numerous fibers, including polyethylene, polyolefin and aramid fibers. Many such prior art laminates are woven of various fibers, such as aramid fibers sold under the trademark "Kevlar".
A ballistic non-woven laminate referred to by the trademark Spectra-Shield is manufactured by Allied-Signal, Inc. The laminate structure is used in soft body armor to protect the wearer against high-velocity bullets and fragments. Spectra-Shield is made by first forming a non-woven unidirectional tape, composed of unidirectional polyethylene fibers and an elastic resin material that holds the fibers together. The resin penetrates to the filament level, impregnating the entire structure with the resin product. Two layers, or arrays, of the unidirectional tape are then laminated together (cross-plied) at right angles to form a panel. Then, the panel is covered on both sides with a thin film of polyethylene on the order of 0.001 inches thick. The film prevents adjacent panels from sticking together when the panels are layered together in the soft body armor.
The present invention relates to an improved non-woven ballistic laminate structure. Enhanced anti-ballistic characteristics are obtained while optimizing use of materials in the laminate. Specifically, it has been determined that ballistic laminates can be constructed of high performance fibers without using resins to hold the fibers together. This substantially reduces the weight of the structure without compromising the anti-ballistic characteristics of the structure. As used in this application, the term "high performance fiber" refers to fibers having a tensile strength greater than 7 grams per denier.
By omitting the resin, the cross-plied arrays of fibers directly contact each other, instead of being encapsulated and therefore separated from each other by the resin. An ultra-thin film is used both to cover the cross-plied arrays and to hold the arrays to each other.
The prior art teaches that a critical limit of 80% fiber must be maintained in the laminate in order to maintain product integrity. If the percentage of resin, covers and the like exceeds 20%, the anti-ballistic qualities of the laminate begin to degrade.
This invention incorporates certain features heretofore recognized as being only applicable to older, low performance fibers into the field of high performance fibers in order to achieve a ballistic laminate structure with enhanced anti-ballistic characteristics.